Lubricating compositions



Patented Mar. 4, 1952 UNITED STATES PATENT OFFI or. I

LUBRICATING COMPOSITIONS Arnold J. Morway, Rahway, and Paul V. Smith, Jr., Westfield, N. .L, assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application August 2, 1950,

Serial No. 177,347

8 Claims. (01. 252-42 This invention relates to new and useful lubricating compositions. Particularly, the invention relates to lubricating grease compositions having desirable extreme pressure resistant characteristics and low temperature properties. More particularly, this invention relates to a lubricating grease composition prepared by thickening to a grease consistency with the lithium soap of a substantially saturated fatty acid a lubricating oil containing atleast a minor proportion of R-z- -Y-o-z-R wherein Y may be either a divalent aliphatic hydrocarbon radical containingfrom 2 to 8 carbon atoms or a divalent aliphatic hydrocarbon radical containing from 2 to 8 carbon atoms with a thioether linkage therein; Z may be either oxygen or sulfur; and R may be monovalent hy-. drocarbon radicals alike or different and con taining a total of from 14 to 40 carbon atoms; It is to be seen that when Z is oxygen Y must, of

necessity, contain sulfur to answer the general description of a sulfur-containing ester of a dibasic acid. When Z is sulfur, however, Y is preferably a hydrocarbonradical' It is to be seen then that the type compounds described by the formula above includes thio ethers when Y contains sulfur and thioesters when Y is an aliphatic hydrocarbon radical. Listed among the thioesters of dibasic acids operable in thebasic concept of this invention are di-tert.-octyl thioadipate, tert.-octyl n-octyl thioadipate, di-tert.-octyl thiosebacate, di-tert.-dodecyl thiosuccinate, iso-octyl tert.-dodecyl thioadipate, n-hexyl tort-decyl thioadipate, iso; hexyl tert.-dodecyl thiosuccinate. Amongthe operable thioethers of dibasic acid esters that are operable in this invention are such compounds as iso-octyl beta-thiodipropionate, iso-octyl thiodiglycolate, iso-hexyl iso-decyl beta-thiodipro pionate, iso-octyl ester of -thial,9-nonanedioic acid, 2,6-di-methy1-4-thia-1L7-heptanedioic acid. 4.7-di-thia-LIO-decanedioic;acid.

In either instance, thesum of the R groups must contain a total of from 14 to 40 carbon atoms in order to impart sufficient non-volatility to the compound. A straight chain or slightly branched chain alcohol containing the requisite number of carbon atoms may be used to esterify the carboxylic groups. Especially operable are the alcohols obtained from the so-called Oxo" process now well described in the patent literature.

Generally speaking, a novel grease composition of this invention may be prepared by the following procedure: l

About of the synthetic oil, or of a blend containing the synthetic oil. is admixed with the desired amount of a preformed soap solution and the soap dispersed as a slurry without heating. The balance of the synthetic oil or blend is then added and the mixture heated with stirring to about 400 F. Additional additive ma-- terials, if desired, are added to the mixture at;

this point and formulation chilled rapidly by means of a drum type cooler or in shallow pans resulting in a translucent grease of excellent appearance.

As the soap or thickening constituent of the grease compositions of this invention it is preferred to use the lithium soap of any of the well known soap making materials such hydrogenated fish oil acids, stearic acid, oleic acid, hydroxy stearic, acid, beef fat, tallow, saturated or unsaturated glycerides of various fatty acids, or mixtures of the above in any preparation. The formulation will be adjusted, in the preferred embodiment, so that from 10% to 30% by weight of the lithium soap will be incorporated with the oil constituent. If it is desired, the soap may be formed in situ in a small amount of an unhydrolyzable material such as mineral; oil by chargingv to the grease kettle the calculated amounts of the acidic material and adding thereto a solution of lithium hydroxide. The reaction and dehydration of the soap formed occurs in the unhydrolyzable and unsaponifiable fluid e. g. mineral oil. It is also within the contemplation of this invention to admix the desired amount of lithium soap with a small amount of a mineral oil, thereafter adding the sulfurcontaining dibasic acid ester.

Although it is preferred to utilize as the soap dispersant the dibasic acid esters containing sulfur as prescribed above, it has also been found that excellent grease formulations having desirable extreme pressure and low temperature properties may be made so long as there is present about 25% or more of the sulfur-containing-dif basic acid esters in the oil base. The remaining percentage of the oil base may be a natural occurring mineral oil or other synthetic oils such as the polyglyools, polyglycol ether, polyglycol esters, alkylated aromatics, polymerized cracked wax, long chain esters, esters of dibasic esters such as sebacates or adipates which do not contain sulfur, glycol esters of hexanoic acid and the like.

As was mentioned above, additive materials to further improve the properties of the final product, such as oxidation inhibitors and the like, may be added to the greases of this invention.

As a more detailed explanation of the concept of this invention, the following examples are given. These examples, of course, are restricted to specific constituents, of necessity, and are not to be taken as limiting the concept of this invention as outlined above.

Example I A grease having the following composition was prepared 21.75% lithium stearate 0.50% phenol alpha naphthylamine 1.25% amine type oxidation inhibitor 76.50% iso-octyl thiodipropionate The lithium stearates and about 50% of the ester was admixed in a cold steam heated grease kettle and the temperature then raised gradually with stirring to 90 F. At this point the balance of the'e-ster and the oxidation inhibitors were added and heating continued until 40011". The formulation was then chilled and then cooled rapidly by pouring into shallow pans. An excellent homogenous hard smooth cake was obtained.

, After 60 strokes using the ASTM fine hole worker plate the stanadard ASTM penetration test gave a penetration of 275 mm./l0. grease was then worked for 100,000 strokes using the same fine hole worker plate, retested according to the standard ASTM procedure and gave a penetration of 340 mm./ 10. This test result illustrates the excellent structural stability of this grease composition.

Evaporation tests on two samples of the grease The of Example I were submitted to the Army-Navy H Evaporation Test. This test was run in accordance with the method described on page 11 of Army-Navy Aeronautical Specification Grease; Low Temperature Aircraft Lubricating (Low Volatility Type) AN-G-25.

The grease of Example I above was submitted to a low temperature torque test as described by the Army-Navy Aeronautic a Specification AN-G- 25. In this test a 204K Conrad type 8-ball bearing, in a cold box capable of holding thetemperature variation of the bearing during the test to not more than i1.8 F. was packed with 3 g. of the grease. The packed bearing was inserted in the cold box and the temperature lowered to 67 F. Following the procedure outlined in the AN-G-25 specification on page '7, the results of the-test runs-were as follows: One revolution of the bearingin 'LO'secondand 0.8 second in duplicate runs. i

"The grease of Example 'I was submitted to the gradual loading Almen testing machine. The full weights of the test machine were easily carried by this grease and an unusually loyv frictional (torque) gage reading of 26 was observed. The pin was in 'an excellent condition retaining :its smooth polished surface. "This compares favor Results of the duplicate runs were 0.4% and 0.6% evaporation.

ably with the 1 to 3 weights carried by conventional mineral oil base greases and 4 to 6 weight with di-ester (non-sulfuric) greases.

Example II Following the procedure that is outlined in Example I above, a grease having the following formulation was prepared:

% lithium hydroxystearate 80% di-tert.-octyl thioadipate The final product was an excellent soft grease having the following characteristics:

ASTM worked penetration (mm/10)- '60 strokes 320 50,000 strokes 340 Example III A lubricating grease having the following formodulation was prepared in accordance with the procedure described in Example I:

68.50% di-2-ethylhexy1 sebacate 17.50% di-tert.-octyl thioadipate 7% lithium stearate 7% lithium hydroxystearate This composition, when cooled by rapid chilling in thin layers, gave a smooth translucent grease of excellent appearance. Its excellent structure stability is shown by the following:

ASTM worked penetrations (mm./ 10) 60 strokes 290 50,000 strokes 320 which contains at least by weight of a sulfurcontaining ester of .a dibasic acid, the sulfur being contained in either an ester or ether linkage.

What is claimed is: 1. A lubricating composition consisting essentially of a lubricating oil containing at least 25% by weight based on the total composition of a sulfur-containing ester of a dibas-ic acid having the general formula:

wherein- Y is a radical selected from the group consisting fof divalent aliphatic "hydrocarbon radicals containing from '2 to 8 carbon atoms and divalent aliphatic hydrocarbon radicals containing from 2 to 8 carbon atoms and having a thioether linkage therein, R is an aliphatic hydrocarbon radical containing from 8 to 20 carbon atoms, the sum of R+R being from 14 to 40,, Z is a material of the class consisting of oxygen. and sulfur, when sulfur. :3? being a di U valent aliphatic hydrocarbon radical containing from 2 to 8 carbon atoms per molecule, thickened to a grease consistency with the lithium soap of a substantially saturated fatty acid.

2. A lubricating composition consisting essentially of a synthetic lubricating oil thickened to a grease consistency with from 10 to 30% by weight of a lithium soap of a substantially saturated high molecular weight fatty acid, said synthetic lubricating oil having the following formula:

o R-z- -Y- ZR wherein Y is a radical selected from the group consisting of divalent aliphatic hydrocarbon radicals containing from 2 to 8 carbon atoms and divalent aliphatic hydrocarbon radicals containing from 2 to 8 carbon atoms and having a thioclaim 2 wherein Z is oxygen and Y is a divalent aliphatic hydrocarbon radical containing from 2 to 8 carbon atoms and having therein a thinether linkage.

5. A lubricating composition according to claim 1 wherein said synthetic oil is ditert.-octy1thioadipate.

6. A lubricating composition according to claim 2 wherein said synthetic oil is di-tert.-octyl thioadipate.

7. A lubricating composition according to claim 1 wherein said synthetic oil is di-iso-octyl thiodipropionate.

8. A lubricating composition according to claim 2 wherein said synthetic oil is di-iso-octyl thiodipropionate.

ARNOLD J. MORWAY. PAUL V. SMITH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL CONTAINING AT LEAST 25% BY WEIGHT BASED ON THE TOTAL COMPOSITION OF A SULFUR-CONTAINING ESTER OF A DIBASIC ACID HAVING THE GENERAL FORMULA: 